$ git clone -n https://src.fedoraproject.org/rpms/mozjs128.git /var/lib/mock/f41-build-858862-168494/root/chroot_tmpdir/scmroot/mozjs128
Cloning into '/var/lib/mock/f41-build-858862-168494/root/chroot_tmpdir/scmroot/mozjs128'...
$ git fetch origin caae92fd933644982ed282615968b6e59a4f4c33:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/mozjs128
 * [new ref]         caae92fd933644982ed282615968b6e59a4f4c33 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at caae92f mozjs128-128.3.0 (RHBZ#2315674)